Abstract

Studies of reproduction among chimpanzees traditionally have focused on the mating strategies of males. However, less is known about the mating strategies of female chimpanzees and whether they demonstrate mate choice. I investigated sexual behavior and female mate preference in the chimpanzees of the Kanyawara community. To estimate mate preferences, I analyzed female proceptivity and resistance rates of 6 estrous females toward a total of 13 males as well as male solicitation and aggression rates toward females. Males solicited some females more often than others for mating and preferred them throughout estrus, not only during the periovulatory period (POP), when conception was most likely. In contrast, though females had strong mate preferences in both non-POP and POP, their mate preferences were not consistent between the 2 phases. The shift in mate preferences is evidence of a promiscuous yet tactical mating strategy to confuse paternity. Further, females were more proceptive and generally less resistant toward eschewed males in non-POP and more proceptive and less resistant toward preferred males in POP. Hence, the results indicate that females attempted to mate selectively during the fertile phase. Kanyawara female chimpanzees appear to change their mating strategies and selectivity during estrus and thus may pursue a mixed reproductive strategy. The tactic may allow females to deceive males, indicating that promiscuity among chimpanzee females may be more strategic than previously thought.

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Acknowledgments

I thank the Uganda National Council for Science and Technology, the Uganda Wildlife Authority, and the Makerere University Biological Field Station for permission to conduct this research, especially Gilbert Isabirye-Basuta and John Kasenene. I thank Richard Wrangham for inviting me to study chimpanzees at Kanyawara, for his guidance and his constant encouragement. I also thank Karl Grammer for supervising my study and for his support and enthusiasm. For tracking chimpanzees and long working hours, I thank the late Barwogeza John, Katongole Christopher, Mugurusi Francis, the late Muruuli Christopher, the late Muhangyi Donor, and Tuhairwe Peter. Thanks go to Charlotte Hemelrijk, who kindly pointed out my missing value problem in social matrices, and Han de Vries, who solved the problem with great enthusiasm. I acknowledge Max Kauer for his help to untangle a statistical knot. Further, I thank Melissa Emery Thompson and Rebecca Stumpf for inviting me to the IPS Symposium. Additional thanks go to Thomas Bodendorfer, Kim Duffy, Melissa Emery Thompson, Christine Hrubesch, Marianne Imhof, Martin Muller, Amy Pokempner, and Signe Preuschoft for comments and discussions on the manuscript. The Bureau for International Studies, University of Vienna, and the Österreichische Forschungsgemeinde provided financial support. Finally, I thank Rebecca Stumpf and reviewers for very helpful comments of an earlier version of the manuscript, which greatly improved it.

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